U.S. patent application number 15/735780 was filed with the patent office on 2018-05-24 for illumination device.
This patent application is currently assigned to Dai Nippon Printing Co., Ltd.. The applicant listed for this patent is Dai Nippon Printing Co., Ltd.. Invention is credited to Makio KURASHIGE.
Application Number | 20180142840 15/735780 |
Document ID | / |
Family ID | 57586492 |
Filed Date | 2018-05-24 |
United States Patent
Application |
20180142840 |
Kind Code |
A1 |
KURASHIGE; Makio |
May 24, 2018 |
ILLUMINATION DEVICE
Abstract
An illumination device (10) includes: a light diffusion device
(50) including element diffusion devices (55) that diffuse incident
light; a coherent light source (15) that emits coherent light; a
shaping optical system (20) that shapes the coherent light; a
scanner (30) that adjusts a traveling direction of the coherent
light so as to allow the coherent light to scan the light diffusion
device; and a light condensing optical system located on a light
path of the coherent light from the shaping optical system up to
the light diffusion device. The light condensing optical system
condenses the coherent light such that a spot area on the light
diffusion device is smaller than the element diffusion device. Each
element diffusion device diffuses the coherent light incident
thereon so as to illuminate an element illumination area
corresponding to the element diffusion device.
Inventors: |
KURASHIGE; Makio; (Tokyo,
JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Dai Nippon Printing Co., Ltd. |
Tokyo |
|
JP |
|
|
Assignee: |
Dai Nippon Printing Co.,
Ltd.
Tokyo
JP
|
Family ID: |
57586492 |
Appl. No.: |
15/735780 |
Filed: |
June 22, 2016 |
PCT Filed: |
June 22, 2016 |
PCT NO: |
PCT/JP2016/068527 |
371 Date: |
December 12, 2017 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G02B 26/12 20130101;
F21S 41/16 20180101; F21K 9/233 20160801; G03H 1/2286 20130101;
G03H 2001/2223 20130101; G03H 2001/2292 20130101; F21V 5/02
20130101; F21V 5/04 20130101; F21K 9/60 20160801; G03H 2001/2218
20130101; G02B 27/48 20130101; F21S 41/176 20180101 |
International
Class: |
F21K 9/233 20060101
F21K009/233; F21K 9/60 20060101 F21K009/60; G02B 27/48 20060101
G02B027/48 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 22, 2015 |
JP |
2015-124992 |
Jun 22, 2015 |
JP |
2015-124997 |
Claims
1. An illumination device comprising: a light diffusion device
including element diffusion devices that diffuse incident light; a
coherent light source that emits coherent light; a shaping optical
system that shapes the coherent light; a scanner that adjusts a
traveling direction of the coherent light so as to allow the
coherent light to scan the light diffusion device; and a light
condensing optical system located on a light path of the coherent
light from the shaping optical system up to the light diffusion
device; wherein: the light condensing optical system condenses the
coherent light such that a spot area on the light diffusion device
is smaller than the element diffusion device; and each element
diffusion device diffuses the coherent light incident thereon so as
to illuminate an element illumination area corresponding to the
element diffusion device.
2. The illumination device according to claim 1, wherein: the
shaping optical system divides the coherent light emitted from the
coherent light source into light fluxes; and the light condensing
optical system adjusts light paths of the light fluxes such that
the light fluxes are overlapped at least partially on the light
diffusion device.
3. The illumination device according to claim 1, wherein the light
condensing optical system includes a lens, and the light diffusion
device is located on a focus position of the lens.
4. The illumination device according to claim 1, wherein the
shaping optical system includes a collimation lens, and a lens
array located on a light path from the collimation lens up to the
light condensing optical system.
5. The illumination device according to claim 4, wherein: the lens
array includes element lenses; and light fluxes emergent from the
element lenses have the same light distributions.
6. The illumination device according to claim 1, wherein the
shaping optical system has a beam homogenizer.
7. The illumination device according to claim 1, further comprising
an emission control unit that controls emission of the coherent
light from the coherent light source.
8. The illumination device according to claim 7, wherein the
emission control unit controls emission of the coherent light of
the coherent light source, depending on an irradiation position of
the coherent light on the light diffusion device.
9. The illumination device according to claim 1, wherein: the light
diffusion device has a hologram storage medium; and the element
diffusion devices are element holograms having interference fringe
patterns different from one another.
10. The illumination device according to claim 1, wherein: the
light diffusion device has a lens array group including a plurality
of lens arrays; and the element diffusion devices have the lens
arrays.
11. An illumination device comprising: a light deflection device
including element deflection devices that adjust a traveling
direction of incident light; a light source; a diffusion optical
system that diffuses light-source light emitted by the light
source; a scanner that adjusts a traveling direction of the
light-source light so as to so as to allow the light-source light
to scan the light deflection device; and a light condensing optical
system located on a light path of the light-source light from the
diffusion optical system up to the light deflection device;
wherein: the light condensing optical system condenses the
light-source light such that a spot area on the light deflection
device is smaller than the element deflection device; and each
element deflection device adjusts a traveling direction of the
light-source light incident thereon so as to illuminate an element
illumination area corresponding to the element deflection
device.
12. The illumination device according to claim 11, wherein: the
diffusion optical system divides the light-source light into light
fluxes; and the light condensing optical system adjusts light paths
of the light fluxes such that the light fluxes are overlapped at
least partially on the light deflection device.
13. The illumination device according to claim 11, wherein the
light condensing optical system includes a lens, and the light
deflection device is located on a focus position of the lens.
14. The illumination device according to claim 11, wherein the
diffusion optical system includes a collimation lens, and a lens
array located on a light path from the collimation lens up to the
light condensing optical system.
15. The illumination device according to claim 14, wherein: the
lens array includes element lenses; and light fluxes emergent from
the element lenses have the same light distributions.
16. The illumination device according to claim 11, wherein the
diffusion optical system has a beam homogenizer.
17. The illumination device according to claim 11, further
comprising an emission control unit that controls emission of light
from the light source.
18. The illumination device according to claim 17, wherein the
emission control unit controls emission of light from the light
source, depending on an irradiation position of the light-source
light on the light deflection device.
19. The illumination device according to claim 11, wherein: the
light deflection device has a diffraction grating array; and each
element deflection device is a diffraction grating.
20. The illumination device according to claim 11, wherein: the
light deflection device has a prism array; and each element
deflection device is a prism.
Description
TECHNICAL FIELD
[0001] The present invention relates to an illumination device that
illuminates a predetermined area by using light.
BACKGROUND ART
[0002] As disclosed in JP2012-146621A, for example, an illumination
device using a coherent light source is widely used. A laser light
source that oscillates laser light (laser beam) is typically used
as the coherent light source.
[0003] JP2012-146621A discloses a vehicle lighting tool. The
vehicle lighting tool includes a light source, which can be formed
by a laser oscillation device, and four hologram devices. The
respective hologram devices are moved by a rotating and driving
apparatus to be located on positions where they can receive laser
light from the light source. The respective hologram devices
diffract the laser light to achieve illumination in a desired light
distribution pattern. By suitably selecting a hologram device which
is irradiated with laser light, illumination in a predetermined
light distribution pattern can be achieved. In the vehicle lighting
tool, in order to prevent that an unintended area is irradiated
with illumination light, it is necessary to control irradiation of
laser light while the locations of the four hologram devices are
changed. In this case, a period of time in which the light source
stops emission of light becomes long. Thus, it is impossible to
sufficiently utilize performance of the light source so as to
illuminate an illumination area with a sufficiently bright quantity
of light.
DISCLOSURE OF INVENTION
[0004] The present invention has been made in consideration of the
above point. The first object of the present invention is to
provide an illumination device that can sufficiently utilize
performance of a coherent light source so as to brightly illuminate
an illumination area in a desired light distribution pattern.
[0005] In addition, the present invention has been made in
consideration of the above point, and the second object thereof is
to provide an illumination device that can sufficiently utilize
performance of a light source, which is not limited to a coherent
light source, so as to brightly illuminate an illumination area in
a desired light distribution pattern.
[0006] An illumination device according to a first embodiment of
the present invention is an illumination device comprising:
[0007] a light diffusion device including element diffusion devices
that diffuse incident light;
[0008] a coherent light source that emits coherent light;
[0009] a shaping optical system that shapes the coherent light;
[0010] a scanner that adjusts a traveling direction of the coherent
light so as to allow the coherent light to scan the light diffusion
device; and
[0011] a light condensing optical system located on a light path of
the coherent light from the shaping optical system up to the light
diffusion device;
[0012] wherein:
[0013] the light condensing optical system condenses the coherent
light such that a spot area on the light diffusion device is
smaller than the element diffusion device; and
[0014] each element diffusion device diffuses the coherent light
incident thereon so as to illuminate an element illumination area
corresponding to the element diffusion device.
[0015] In the illumination device according to the first embodiment
of the present invention,
[0016] the shaping optical system may divide the coherent light
emitted from the coherent light source into light fluxes; and
[0017] the light condensing optical system may adjust light paths
of the light fluxes such that the light fluxes are overlapped at
least partially on the light diffusion device.
[0018] In the illumination device according to the first embodiment
of the present invention, the light condensing optical system may
include a lens, and the light diffusion device may be located on a
focus position of the lens.
[0019] In the illumination device according to the first embodiment
of the present invention, the shaping optical system may include a
collimation lens, and a lens array located on a light path from the
collimation lens up to the light condensing optical system.
[0020] In the illumination device according to the first embodiment
of the present invention,
[0021] the lens array may include element lenses; and
[0022] light fluxes emergent from the element lenses may have the
same light distributions.
[0023] In the illumination device according to the first embodiment
of the present invention, the shaping optical system may have a
beam homogenizer.
[0024] The illumination device according to the first embodiment of
the present invention may further comprise an emission control unit
that controls emission of the coherent light from the coherent
light source.
[0025] In the illumination device according to the first embodiment
of the present invention, the emission control unit may control
emission of the coherent light of the coherent light source,
depending on an irradiation position of the coherent light on the
light diffusion device.
[0026] In the illumination device according to the first embodiment
of the present invention,
[0027] the light diffusion device may have a hologram storage
medium; and
[0028] the element diffusion devices may be element holograms
having interference fringe patterns different from one another.
[0029] In the illumination device according to the first embodiment
of the present invention,
[0030] the light diffusion device may have a lens array group
including a plurality of lens arrays; and
[0031] the element diffusion devices may have the lens arrays.
[0032] According to the first embodiment of the present invention,
the illumination device can sufficiently utilize performance of the
coherent light source so as to brightly illuminate an illumination
area in a desired light distribution pattern.
[0033] An illumination device according to a second embodiment of
the present invention is an illumination device comprising:
[0034] a light deflection device including element deflection
devices that adjust a traveling direction of incident light;
[0035] a light source;
[0036] a diffusion optical system that diffuses light-source light
emitted by the light source;
[0037] a scanner that adjusts a traveling direction of the
light-source light so as to allow the light-source light to scan
the light deflection device; and
[0038] a light condensing optical system located on a light path of
the light-source light from the diffusion optical system up to the
light deflection device;
[0039] wherein:
[0040] the light condensing optical system condenses the
light-source light such that a spot area on the light deflection
device is smaller than the element deflection device; and
[0041] each element deflection device adjusts a traveling direction
of the light-source light incident thereon so as to illuminate an
element illumination area corresponding to the element deflection
device.
[0042] In the illumination device according to the second
embodiment of the present invention,
[0043] the light diffusion optical system may divide the
light-source light into light fluxes; and
[0044] the light condensing optical system may adjust light paths
of the light fluxes such that the light fluxes are overlapped at
least partially on the light deflection device.
[0045] In the illumination device according to the second
embodiment of the present invention, the light condensing optical
system may include a lens, and the light deflection device may be
located on a focus position of the lens.
[0046] In the illumination device according to the second
embodiment of the present invention, the diffusion optical system
may include a collimation lens, and a lens array located on a light
path from the collimation lens up to the light condensing optical
system.
[0047] In the illumination device according to the second
embodiment of the present invention,
[0048] the lens array may include element lenses; and
[0049] light fluxes emergent from the element lenses may have the
same light distributions.
[0050] In the illumination device according to the second
embodiment of the present invention, the diffusion optical system
may have a beam homogenizer.
[0051] The illumination device according to the second embodiment
of the present invention may further comprise an emission control
unit that controls emission of the light from the light-source.
[0052] In the illumination device according to the second
embodiment of the present invention, the emission control unit may
control emission of light from the light-source, depending on an
irradiation position of the light-source light on the light
deflection device.
[0053] In the illumination device according to the second
embodiment of the present invention,
[0054] the light deflection device may have a diffraction grating
array; and
[0055] each element deflection device may be diffraction
grating.
[0056] In the illumination device according to the second
embodiment of the present invention,
[0057] the light deflection device may have a prism array; and
[0058] each element deflection device may be prism.
[0059] According to the second embodiment of the present invention,
the illumination device can sufficiently utilize performance of the
light-source so as to brightly illuminate an illumination area in a
desired light distribution pattern.
BRIEF DESCRIPTION OF DRAWINGS
[0060] FIG. 1 is a perspective view schematically showing an
overall structure of an illumination device, for explaining a first
embodiment of the present invention.
[0061] FIG. 2 is a plan view showing the illumination device of
FIG. 1.
[0062] FIG. 3 is a plan view showing a scanner, a light condensing
optical system and a light diffusion device of the illumination
device of FIG. 1, mainly for explaining a function of the light
condensing optical system.
[0063] FIG. 4 is a view showing the light diffusion device and an
illumination area that is illuminated with diffusion light from the
light diffusion device in the illumination device of FIG. 1, for
explaining a function of the light diffusion device.
[0064] FIG. 5 is a plan view showing a spot area on the light
diffusion device.
[0065] FIG. 6 is a plan view showing the spot area on the light
diffusion device, with a shaping optical system and the light
condensing optical system being omitted.
[0066] FIG. 7 is a perspective view schematically showing an
overall structure of an illumination device, for explaining a
second embodiment of the present invention.
[0067] FIG. 8 is a plan view showing the illumination device of
FIG. 7.
[0068] FIG. 9 is a plan view showing a scanner, a light condensing
optical system and a light deflection device of the illumination
device of FIG. 7, mainly for explaining a function of the light
condensing optical system.
[0069] FIG. 10 is a plan view showing the light deflection device
of the illumination device of FIG. 7.
[0070] FIG. 11 is a view showing the light deflection device and an
illumination area that is illuminated with light from the light
deflection device in the illumination device of FIG. 7.
[0071] FIG. 12 is a plan view showing a spot area on the light
deflection device.
[0072] FIG. 13 is a plan view showing the spot area on the light
deflection device, with a diffusion optical system and the light
condensing optical system being omitted.
MODE FOR CARRYING OUT THE INVENTION
[0073] Embodiments of the present invention will be described
herebelow with reference to the drawings. In the drawings attached
to the specification, a scale size, an aspect ratio and so on are
changed and exaggerated from the actual ones, for the convenience
of easiness in illustration and understanding
[0074] Further, terms specifying shapes, geometric conditions and
their degrees, e.g., "parallel", "perpendicular/orthogonal",
"same", etc., are not limited to their strict definitions, but are
to be construed to include a range capable of exerting a similar
function.
[0075] A first embodiment is firstly described with reference to an
example shown in FIGS. 1 to 6.
[0076] FIG. 1 is a perspective view schematically showing an
overall structure of an illumination device 10. The illumination
device 10 illuminates an illumination area Z by using coherent
light. The illumination device 10 includes a laser light source 15
functioning as a coherent light source. The laser light source 15
oscillates laser light (laser beam) which is an example of coherent
light. The illumination device 10 includes a shaping optical system
20, a scanner 30, a light condensing optical system 40 and a light
diffusion device 50, which process light emitted from the laser
light source 15. In the example shown in FIG. 1, the shaping
optical system 20, the scanner 30, the light condensing optical
system 40 and the light diffusion device 50 are located in this
order along a light path of laser light from the laser light source
15, and they process laser light in this order. As described in
detail below, the illumination device 10 described herein can
illuminate, with a large quantity of light, the illumination area Z
in a desired light distribution pattern, while sufficiently
utilizing the performance of the coherent light source by means of
optical actions in the shaping optical system 20 and the light
condensing optical system 40. Herebelow, the respective constituent
elements are sequentially described.
[0077] In the example shown in FIG. 1, the laser light source 15
has a plurality of light source units 17 that emit laser light. The
light source units 17 may be independently arranged, or may be a
light source module formed by arranging the light source units 17
side by side on a common substrate. For example, the light source
units 17 have a first light source unit 17a that oscillates light
of a red emission wavelength range, a second light source unit 17b
that oscillates light of a green emission wavelength range, and a
third light source unit 17c that oscillates light of a blue
emission wavelength range. According to this example, since three
laser lights (laser beams) emitted from the light source units 17a,
17b and 17c are overlapped, illumination beams of various colors
including a white illumination beam can be generated.
[0078] Although an example in which the laser light source 15 has
the three light source units 17a, 17b and 17c having emission
wavelength ranges different from one another is described
herebelow, the present invention is not limited thereto. The laser
light source 15 may have two light units 17 having emission
wavelength ranges different from each other, or four or more light
units 17 having emission wavelength ranges different from one
another. In addition, in order to increase emission intensity, a
plurality of the light source units 17 may be provided for each
emission wavelength range.
[0079] As shown in FIG. 1, the illumination device 10 includes an
emission control unit 12 connected to the laser light source 15.
The emission control unit 12 controls emission timings of laser
lights (laser beams) emitted by the laser light source 15. In
particular, the emission control unit 12 can switch emission of
laser lights and stop of emission of laser lights from the light
source unit 17a, 17b or 17c, independently from other light source
units. The control of emitting or not emitting laser lights by the
emission control unit 12 is carried out based on scanning timings
of a plurality of laser lights by the scanner 30, in other words,
based on incident positions of laser lights on the light diffusion
device 50. As described above, in the case where the laser light
source 15 can emit three laser lights, i.e., a red laser light, a
blue laser light and a green laser light, it is possible to
generate illumination light of a color that is a combination of
given two or more colors of red, blue and green, by controlling an
emission timing of each laser light.
[0080] The emission control unit 12 may control whether a laser
light is emitted from each light source unit 17 or not, i.e.,
ON/OFF of emission, or may switch blocking or not blocking of a
light path of a laser light having been emitted from each light
source unit 17. In the latter case, light shutter units, not shown,
may be disposed between the respective light source units 17 and
the shaping optical system 20, such that passage and blockage of
laser light can be switched by the light shutter units.
[0081] Next, the shaping optical system 20 is described. The
shaping optical system 20 shapes laser light emitted from the laser
light source 15. In other words, the shaping optical system 20
shapes a cross-sectional shape of laser light orthogonal to an
optical axis, and a three-dimensional shape of a light flux of
laser light.
[0082] FIG. 2 is a plan view showing the illumination device 10. As
shown in FIG. 2, the shaping optical system 20 includes a beam
expander 21, a collimation lens 22 and a lens array 23, in this
order along a light path of laser light. The beam expander 21
shapes a laser light emitted from the laser light source 15 into a
divergent light flux. The collimation lens 22 reshapes the
divergent light flux generated by the beam expander 21 into
parallel light fluxes lf1. The lens array 23 includes a plurality
of element lenses 24 that are arranged on positions facing the
collimation lens 22. The element lenses 24 are positioned such that
an optical axis d.sub.24 of each element lens 24 is parallel to an
optical axis d.sub.22 of the collimation lens 22. In addition, the
element lenses 24 are arranged on a virtual face vl that is
orthogonal to the optical axis d.sub.22 of the collimation lens 22.
Each element lens 24 shapes a parallel light flux lf1, which has
been shaped by the collimation lens 22 and has entered the element
lens 24, into a convergent light flux lf2.
[0083] In the example shown in FIG. 2, the shaping optical system
20 divides a laser light emitted from the laser light source 15
into a plurality of light fluxes lf2. The shaping optical system 20
divides a laser light into light fluxes lf2 the number of which is
equal to the number of the element lenses 24 included in the lens
array 23. In the illustrated example, each element lens 24 shapes a
parallel light flux lf1, which has been shaped by the collimation
lens 22 and has entered the element lens 24, into a convergent
light flux lf2. That is to say, respective light fluxes lf2 divided
by the shaping optical system 20 are convergent light fluxes. In
addition, in the illustrated example, the element lenses 24 have
the same structures each other. Thus, light fluxes lf2 emitted from
the element lenses 24 are the same light distributions. For
example, the light fluxes lf2 have the same convergent angles and
the same convergent positions, and optical axes d.sub.lf2 of the
light fluxes lf2 are parallel to one another.
[0084] A plurality of the shaping optical systems 20 may be
provided correspondingly to the respective light source units 17
included in the laser light source 15. Alternatively, the single
shaping optical system 20 capable of adjusting light paths of laser
lights from the light source units 17a, 17b and 17c may be
provided. In the example shown in FIG. 2, the light source units
17a, 17b and 17c may be aligned in the depth direction of the sheet
plane of FIG. 2, the beam expander 21 may diverge a laser light
only in a plane of the sheet plane of FIG. 2, and the collimation
lens 22 and the element lenses 24 of the lens array 23 in the
shaping optical system 20 may respectively be formed as cylindrical
lenses extending to have a certain cross-sectional shape in the
depth direction of the sheet plane of FIG. 2. According to this
example, the light source units 17 can share the collimation lens
22 and the lens array 23.
[0085] Next, the scanner 30 is described. The scanner 30 adjusts a
traveling direction of a laser light emitted from the laser light
source 15. The scanner 30 changes a traveling direction of a laser
light over time. Due to the light path adjustment of the scanner
30, a laser light emitted from the laser light source 15 scans the
light diffusion device 50. In the example shown in FIGS. 1 and 2,
the scanner 30 is formed as a polygonal mirror 31 having six
reflection surfaces. When the polygonal mirror 31 is rotated about
its central axis line as a rotational axis line ra, a reflection
direction of light that has entered there from a certain direction
can be changed cyclically. The respective six reflection surfaces
of the polygonal mirror 31 are formed as flat surfaces. Thus, as
shown in FIG. 3, after three light fluxes lf3, which had been
shaped by the shaping optical system 20, have been reflected by the
polygonal mirror 31 so that their traveling directions have been
changed, optical axes d.sub.lf3 of the light fluxes lf3 remain
parallel. FIG. 3 is a partially enlarged plan view showing a light
path from the scanner 30 up to the light diffusion device 50.
[0086] In particular, in the illustrated example, the light source
units 17a, 17b and 17c are aligned in a direction parallel to the
rotational axis line ra of the polygonal mirror 31 (see FIG. 1).
The reflection surface of the polygonal mirror 31 includes, along
this rotational axis line ra, a first reflection unit 31a, a second
reflection unit 31b and a third reflection unit 31c. The first
reflection unit 31a reflects a laser light emitted from the first
light source unit 17a and cyclically changes a traveling direction
of the laser light in a plane orthogonal to the rotational axis
line ra. In addition, the second reflection unit 31b reflects a
laser light emitted from the second light source unit 17b, and the
third reflection unit 31c reflects a laser light emitted from the
third light source unit 17c.
[0087] As shown in FIG. 2, the polygonal mirror 31 is positioned
with respect to the shaping optical system 20, such that the
polygonal mirror 31 reflects light from the shaping optical system
20 on a focus position of each element lens 24 of the lens array
23, or on a position close thereto. Thus, as shown in FIG. 3, light
reflected from the polygonal mirror 31 substantially becomes a
divergent light flux lf3 whose divergent point is the reflection
surface of the polygonal mirror 31.
[0088] The scanner 30 is not limited to the illustrated polygonal
mirror 31. It is possible to use, as the scanner 30, an apparatus
that three-dimensionally changes in a biaxial direction a traveling
direction of light incident thereon from a certain direction. For
example, MEMS (micro electromechanical systems) such as a digital
micromirror device (DMD) may be used as the scanner 30.
[0089] Next, the light condensing optical system 40 is described.
The light condensing optical system 40 is located on a light path
of a laser light from the shaping optical system 20 up to the light
diffusion device 50. The light condensing optical system 40
optically processes a laser light having been shaped by the shaping
optical system 20. The light condensing optical system 40 condenses
the laser light, such that a spot area S on the light diffusion
device 50, i.e., an area, which is irradiated with a laser light on
the light diffusion device 50 at a certain instance, has a smaller
planar dimension.
[0090] In the illustrated example, the light condensing optical
system 40 is formed by a light condensing lens 41 having a focus
Pf. The light condensing lens 41 is located on a light path of a
laser light from the saner 30 toward the light diffusion device 50.
As described above, the shaping optical system 20 divides a laser
light into a plurality of light fluxes lf3. As shown in FIG. 3, the
optical axes d.sub.lf3 of the light fluxes lf3 are parallel to one
another. Thus, as shown in FIG. 3, because of a lens action of the
light condensing lens 41, optical axes d.sub.lf4 of three light
fluxes lf4 intersect on a position Px on a virtual face vlf that is
apart from the light condensing lens 41 by a focus distance
f.sub.40 of the light condensing lens 41 along an optical axis
d.sub.40 of the light condensing lens 41. In the illustrated
example, the light diffusion device 50 is located on the virtual
face vlf that is apart from the light condensing lens 41 by the
focus distance f.sub.40 of the light condensing lens 41 along the
optical axis d.sub.40 of the light condensing lens 41. Thus, the
three light fluxes lf3 having been shaped by the shaping optical
system 20 are overlapped at least partially on the light diffusion
device 50, by the light condensing action of the light condensing
optical system 40.
[0091] In particular, in the illustrated example, as shown in FIG.
3, the scanner 30 and the light condensing optical system 40 are
located such that the polygonal mirror 31 reflects a laser light
from the shaping optical system 20 on a position apart from the
light condensing lens 41 by the focus distance f.sub.40 of the
light condensing lens 41 along the optical axis d.sub.40 of the
light condensing lens 41 or on a position close to the position.
Further, as described above, each of light fluxes lf3, which has
been reflected by the polygonal mirror 31 and has entered the light
condensing optical system 40, is a divergent light flux lf3 whose
divergent point is located on the reflection surface of the
polygonal mirror 31 or close thereto. Thus, each light flux lf3
passes through the light condensing lens 41 so as to be converted
to parallel fluxes lf4. As a result, the light fluxes lf4 having
been shaped by the shaping optical system 20 irradiate the same
area on the light diffusion device 50 by the light condensing
function of the light condensing optical system 40, i.e., the light
fluxes lf4 are overlapped on the light diffusion device 50 highly
precisely. Since the scanner 30 changes traveling directions of
laser lights with time, a spot area S on which the light fluxes lf4
are condensed by the light condensing optical system 40 changes its
position over time on the light diffusion device 50.
[0092] A plurality of the light condensing optical systems 40 may
be provided correspondingly to the respective light source units
17a, 17b and 17c included in the laser light source 15.
Alternatively, the single light condensing optical system 40
capable of adjusting light paths of laser lights from the light
source units 17a, 17b and 17c may be provided. For example, when a
laser light is diverged or converged only in a plane parallel to
the sheet plane of FIG. 3, the light condensing lens 41 forming the
light condensing optical system 40 may be a cylindrical lens
extending to have a certain cross-sectional shape in the depth
direction of the sheet plane of FIG. 2. According to this example,
the light condensing lens 41 can be shared by laser lights emitted
by the light source units 17a, 17b and 17c.
[0093] Next, the light diffusion device 50 is described. The light
diffusion device 50 diffuses a laser light so as to illuminate a
predetermined range. To be more specific, the laser light diffused
by the light diffusion device 50 passes through an illumination
area Z, and then illuminates a predetermined range that is an
actual illumination range.
[0094] The illumination area Z and an element illumination area Zp,
which forms a part of the illumination area Z, are illumination
areas of near fields that are overlappingly illuminated by
respective element diffusion devices 55 in the light diffusion
device 50. An illumination range of a far field is generally
expressed as a diffusion angle distribution in an angular space,
rather than an actual illumination area size. The terms
"illumination area" and "element illumination area" in this
specification include a diffusion angle range in an angular space
in addition to an actual illumination area (illumination range).
Thus, a predetermined range illuminated by the illumination device
10 of FIGS. 1 and 4 can be an area that is greatly larger than the
illumination area Z of a near field shown in FIGS. 1 and 4.
[0095] FIG. 4 is a plan view showing the light diffusion device 50,
together with the illumination area Z to which light is directed by
the light diffusion device 50. In the illustrated example, the
light diffusion device 50 includes a first light diffusion device
50a, a second light diffusion device 50 and a third light diffusion
device 50c, correspondingly to the fact that the laser light source
15 includes the first to third light source units 17a, 17b and 17c.
A laser light from the first light source unit 17a enters the first
light diffusion device 50a, a laser light from the second light
source unit 17b enters the second light diffusion device 50b, and a
laser light from the third light source unit 17c enters the third
light diffusion device 50c. By using the laser lights that have
entered the whole areas of the respective light diffusion devices
50a, 50b and 50c so as to be diffused, the whole area of the common
illumination area Z can be illuminated. Thus, the first light
diffusion device 50a directs red light from the first light source
unit 17a toward the illumination area Z, the second light diffusion
device 50b directs green light from the second light source unit
17b toward the illumination area Z, and the third light diffusion
device 50c directs blue light from the third light source unit 17c
toward the illumination area Z, whereby the illumination area Z can
be illuminated in white. As shown in FIG. 1, the light diffusion
devices 50a, 50b and 50c are respectively formed to have an
elongate shape in a direction orthogonal to the rotational axis
line ra of the polygonal mirror 31 forming the scanner 30. The
light diffusion devices 50a, 50b and 50c are arranged side by side
in a direction orthogonal to their longitudinal directions.
[0096] As shown by the dotted lines in FIG. 4, each of the light
diffusion devices 50a, 50b and 50c has a plurality of element
diffusion devices 55. Each element diffusion device 55 has a light
path control function for directing light, which has been incident
on each area in its incident surface, toward a predetermined
direction depending on a position of the area. The element
diffusion device 55 described herein corrects a traveling direction
of light incident on a given area or a given position, and directs
the light to a predetermined area. Namely, laser lights emitted to
respective areas, which are obtained by planarly dividing the
incident surface of the element diffusion device 55, pass through
the element diffusion device 55, and then illuminate areas that are
at least partially overlapped with each other.
[0097] In the illustrated example, light, which has entered a small
area in the element diffusion device 55 via the scanner 30, is
diffused by the element diffusion device 55 to illuminate the whole
area of a predetermined element illumination area Zp. The element
illumination area Zp forms a part of the illumination area Z. An
element illumination area Zp corresponding to one element diffusion
device 55 is not at least partially overlapped with an element
illumination area Zp corresponding to another element diffusion
device 55. Namely, an aggregation of the element illumination areas
Zp corresponding to a plurality of element diffusion devices 55
provides the illumination area Z that can be illuminated by the
illumination device 10.
[0098] In the example shown in FIG. 4, nine element diffusion
devices 55 are aligned along the longitudinal directions of the
respective light diffusion devices 50a, 50b and 50c. The
illumination area Z is planarly divided like a grid into nine
element illumination areas Zp. That is to say, in the illustrated
example, one element illumination area Zp is not overlapped with
another element illumination area Zp. First element diffusion
devices 55a of the respective light diffusion devices 50a, 50b and
50c illuminate a first element illumination area Zp1. Similarly,
second to ninth element diffusion devices 55b to 55i of the
respective light diffusion devices 50a, 50b and 50c illuminate
second to ninth element illumination areas Zp2 to Zp9.
[0099] Since a traveling direction of a laser light is changed by
the scanner 30 over time, as shown in FIG. 4, the laser lights
(laser beams) scan the light diffusion devices 50a, 50b and 50c
along the longitudinal directions of the light diffusion devices
50a, 50b and 50c. As shown in FIG. 4, an area on the light
diffusion device 50 irradiated with the laser light at a certain
instance, i.e., a spot area S has a planar dimension smaller than
the element diffusion device 55. The spot area S scans the first to
ninth element diffusion devices 55a to 55i sequentially.
[0100] The light diffusion device 50 is formed with the use of a
hologram storage medium 52, for example. In the example shown in
FIGS. 1 and 4, three hologram storage media 52a, 52b and 52c are
disposed correspondingly to the respective light diffusion devices
50a, 50b and 50c. The respective hologram storage media 52a, 52b
and 52c are provided correspondingly to laser lights of different
wavelength ranges. By using laser lights of different wavelength
ranges which have entered the whole area of the respective hologram
storage media 52a, 52b and 52c so as to be diffused, the whole area
of the common illumination area Z can be illuminated.
[0101] Each of the hologram storage media 52a, 52b and 52c is
segmented into a plurality of the element diffusion devices 55. The
respective element diffusion devices 55 are formed of element
holograms 57 storing interference fringe patters different from one
another. A laser light incident on each element hologram 57 is
diffracted by an interference fringe pattern, and illuminates a
corresponding element illumination area Zp in the illumination area
Z. By variously adjusting the interference fringe patterns, a
traveling direction of a laser light that is diffracted by each
element hologram 57, in other words, a traveling direction of a
laser light that is diffused by each element hologram 57 can be
controlled.
[0102] The element hologram 57 can be manufactured by using
scattered light from a real scattering plate as object light, for
example. To be more specific, when a hologram photosensitive
material that is a matrix of the element hologram 57 is irradiated
with reference light and object light of coherent light interfering
with each other, interference fringes by the light interference are
formed on the hologram photosensitive material so that the element
hologram 57 is manufactured. Laser light that is coherent light is
used as reference light, while scattered light of an isotropic
scattering plate, which is available inexpensively, is used as
object light, for example.
[0103] By emitting laser light toward the element diffusion device
55 such that the laser light travels reversely to the light path of
the reference light that was used when the element hologram 57 was
manufactured, a reconstructed image of the scattering plate is
generated on a position where the scattering plate is located, from
which the object light used when the element hologram 57 was
manufactured was generated. When the scattering plate from which
the object light used when the element hologram 57 was manufactured
was generated uniformly scattered light by its surface, the
reconstructed image of the scattering plate obtained by the
hologram 57 is a uniform surface illumination. Thus, an area in
which the reconstructed image of the scattering plate is generated
becomes an element illumination area Zp.
[0104] Instead of being formed by using real object light and
reference light, a complicated interference fringe pattern formed
on each element hologram 57 can be designed by using a computer
based on a wavelength and an incident direction of expected
illumination light to be reconstructed as well as a shape and a
position of an image to be reconstructed. An element hologram 57
thus obtained is also referred to as computer generated hologram
(CGH). In addition, a Fourier conversion hologram in which
respective points on each element hologram 57 have the same
diffusion angle properties may be generated by a computer. Further,
a size and a position of an actual illumination range may be set by
disposing an optical member such as a lens behind an optical axis
of an element illumination area Zp.
[0105] One of the advantages of providing the element hologram 57
as the element diffusion device 55 is that a light energy density
of laser light can be decreased by diffusion. Another advantage is
that the element hologram 57 can be used as a directional surface
light source. In this case, as compared with a conventional lamp
light source (point light source), a luminance on a light source
surface for achieving the same illumination distribution can be
decreased. Thus, safety of laser light can be improved. Namely,
even when a person looks a laser light having passed through the
element illumination area Zp with his/her eyes, the eyes are less
affected as compared with a case in which a person looks a single
point light source with his/her eyes.
[0106] Specifically, the element diffusion device 55 may be a
volume type hologram storage medium using a photopolymer, a volume
type hologram storage medium that stores hologram using a
photosensitive medium containing a silver salt material, or a
relief type (embossing type) hologram storage medium.
[0107] Next, an operation of the illumination device 10 as
structured above is described.
[0108] As shown in FIG. 1, based on a control signal from the
emission control unit 12, the respective light source units 17a,
17b and 17c oscillate laser lights (laser beams) of respective
wavelength ranges. Laser lights going out from the laser light
source 15 firstly travel toward the shaping optical system 20. In
the example shown in FIG. 2, the laser lights of the respective
wavelength ranges are shaped into parallel light fluxes lf1 by the
beam expander 21 and the collimation lens 22 of the shaping optical
system 20. Thereafter, each of the parallel light fluxes lf1 of the
respective wavelength ranges is divided into convergent light
fluxes lf2 by the element lens 24 of the lens array 23. As to the
laser lights of the respective wavelength ranges, the convergent
light fluxes lf2 are similarly shaped, and optical axes d.sub.lf2
of the convergent light fluxes lf2 are parallel to one another.
[0109] The laser lights having been shaped by the shaping optical
system 20, i.e., the convergent light fluxes lf2 travel toward the
polygonal mirror 31 forming the scanner 30. The polygonal mirror 31
is consecutively rotated about the rotational axis line ra. Thus,
an inclination angle of the reflection surface of the polygonal
mirror 31 is cyclically changed within a predetermined angular
area. As a result, a direction of a laser light reflected by the
polygonal mirror 31 cyclically changes.
[0110] As shown in FIG. 2, the polygonal mirror 31 reflects the
convergent light fluxes lf2 on a position where the convergent
light fluxes lf2 converge, or on a position close thereto. Thus,
since the convergent light fluxes lf2 are reflected by the
polygonal mirror 31, the convergent light fluxes lf2 are converted
into divergent light fluxes lf3 whose divergent points are located
on the reflection position of the polygonal mirror 31, or on a
position close thereto. Each of the six reflection surfaces of the
polygonal mirror 31 is large enough to reflect all the convergent
light fluxes lf2 having been shaped by the shaping optical system
20. Thus, as shown in FIG. 3, optical axes d.sub.lf3 of the
divergent light fluxes lf3 that are the laser lights reflected by
the polygonal mirror 31 remain parallel. Since the polygonal mirror
31 reflects the light fluxes lf3 that are in the convergent state,
enlargement of the polygonal mirror 31 can be effectively
avoided.
[0111] In addition, the polygonal mirror 31 includes the first
reflection unit 31a, the second reflection unit 31b and the third
reflection unit 31c, along this rotational axis line ra. Since
these reflection units 31a, 31b and 31c are synchronically
operated, the laser light from the first light source unit 17a, the
laser light from the second light source unit 17b and the laser
light from the third light source unit 17c synchronically change
their traveling directions.
[0112] As shown in FIG. 3, the divergent light fluxes lf3 with
their light paths having been adjusted by the scanner 30 enter the
light condensing optical system 40. The optical axes d.sub.lf3 of
the divergent light fluxes lf3 remain parallel to one another. In
addition, the light diffusion device 50 is located on the focus Pf
of the light condensing lens 41 forming the light condensing
optical system 40. Thus, light fluxes lf4 with their light paths
having been adjusted by the light condensing lens 41 are condensed
by the light condensing lens 41, and their optical axes d.sub.lf4
intersect on the light diffusion device 50. In particular, in the
illustrated example, the reflection position of the polygonal
mirror 31 is located on a focus position behind the light
condensing lens 41, or on a position close thereto. Thus, the light
fluxes lf3 traveling from the polygonal mirror 31 toward the light
condensing lens 41 are converted to parallel light fluxes lf4 by
the lens effect of the light condensing lens 41. The parallel light
fluxes lf4 are overlapped with one another on the light diffusion
device 50.
[0113] An area on which the parallel light fluxes lf4 are
overlapped with one another on the light diffusion device 50, i.e.,
the spot area S scans the light diffusion device 50 along the
longitudinal direction of the elongate light diffusion device 50,
in conjunction with the operation of the scanner 30. As a result,
as shown in FIG. 4, the laser lights sequentially irradiate the
element diffusion devices 55. The laser light incident on each
element diffusion device 55 is diffused by the element diffusion
device 55 so as to illuminate the whole area of an element
illumination area Zp corresponding to the element diffusion device
55.
[0114] The emission control unit 12 controls emission of laser
lights from the light source unit 17, depending on irradiation
positions of laser lights on the light diffusion device 50. Thus,
only a desired element illumination area Zp in the illumination
area Z can be selected and illuminated. In addition, the emission
control unit 12 can control emission of light from the light source
units 17a, 17b and 17c independently. Thus, it is also possible to
illuminate a predetermined element illumination area Zp with light
emitted from one(s) selected from the first light source unit 17a,
the second light source unit 17b and the third light source unit
17c. That is to say, each of the first to ninth element
illumination areas Zp1 to Zp9 included in the illumination area Z
can be adjusted independently from the other element illumination
areas, as to whether illuminated or not, the degree of brightness
and the color of illumination light.
[0115] As disclosed in WO2012/033174A, the use of coherent light
gives rise to generation of speckles. The speckles may be
recognized as a spot pattern to cause physiological discomfort.
[0116] In the illustrated illumination device 10, as shown in FIG.
4, an area on the light diffusion device 50 irradiated with a laser
light at a certain instance, i.e., a spot area S, which is
irradiated with overlapped parallel light fluxes lf4, is smaller
than the element light diffusion device 55. The spot area S moves
in the element diffusion device 55 in conjunction with the
operation of the scanner 30. The element diffusion device 55 is
formed of the element hologram 57 as the hologram storage medium
52, for example, and diffuses light of a predetermined wavelength
range, which has entered a given part thereof from a predetermined
direction or a direction close thereto, so as to illuminate the
whole area of an element illumination area Zp corresponding to the
element diffusion device 55. Thus, while a spot area S moves in one
element diffusion device 55, an incident direction of illumination
light incident on each position of the element illumination area Zp
changes over time. The fast change of incident direction cannot be
dissolved by human eyes, whereby multiplexed coherent light
scattered patterns that are not correlated to one another are
observed by the human eyes. Therefore, speckles generated
correspondingly to the respective scattered patterns are overlapped
and averaged, which is observed by an observer. For this reason,
the speckles can be made unnoticeable in each element illumination
area Zp.
[0117] In order to simplify control of the scanner 30, the scanner
30 is preferably operated such that a laser light can cyclically
scan the whole area of the light diffusion device 50. In the
example shown in FIG. 4, the scanner 30 is preferably operated such
that a laser light scans over the whole lengths of the light
diffusion devices 50a, 50b and 50c along the longitudinal
directions of the light diffusion devices 50a, 50b and 50c. When
only a predetermined element illumination area Zp is desired to be
illuminated, the emission control unit 12 controls emission or stop
of laser light of the laser light source 15, depending on the
operation of the scanner 30, in other words, depending on a
position on the light diffusion device 50 to be irradiated with a
laser light.
[0118] On the other hand, coherent light emitted from a coherent
light source such as a laser light source generally involves
illuminance non-uniformity in a spot area. Generally, as shown in
FIG. 6, the center of the spot area Sp is brightest, and it
gradually darkens toward a periphery of the spot area Sp.
Typically, an illuminance distribution is the Gaussian distribution
from the center of the spot area Sp toward the periphery thereof.
Namely, the spot area Sp has a large rim part of a low illuminance.
Thus, as shown in FIG. 6, an effective scanning section scp1, in
which the whole spot area Sp is located inside one element
diffusion device 55 corresponding to a predetermined element
illumination area Zp, is relatively short. On the other hand, as
shown in FIG. 6, an ineffective scanning section scp2, in which
only a part of the spot area Sp is located within the one element
diffusion device 55, i.e., in the example shown in FIG. 6, the
ineffective scanning section scp2, in which the spot area Sp is
located over two element diffusion devices 55 that are adjacent in
a scanning direction sd, is relatively long. In the example shown
in FIG. 6, the effective scanning section scp1 is significantly
shorter than the ineffective scanning section scp2.
[0119] In the example shown in FIG. 6, when only a predetermined
element illumination area Zp is illuminated, the emission control
unit 12 emits a laser light in such a manner that the center of the
spot area Sp is located within the effective scanning section scp1,
while stops emission of laser light in such a manner that the
center of the spot area Sp is located within the ineffective
scanning section scp2. Thus, when the scanner 30 is operated at a
constant speed, in the example shown in FIG. 6, a time period in
which the emission of laser light is stopped is significantly long.
Namely, the laser light source 15 is not efficiently used. Further,
in order to illuminate an element illumination area Zp sufficiently
brightly by emitting light in a short period of time, it is
necessary to prepare a high output laser light source.
[0120] In order to deal with this problem, the illumination device
10 in the first embodiment is equipped with the shaping optical
system 20 and the scanner 30. The shaping optical system 20 shapes
coherent light emitted from the laser light source 15. The light
condensing optical system 40 is located on a light path of coherent
light from the shaping optical system 20 up to the light diffusion
device 50, and condenses the coherent light such that the spot area
S on the light diffusion device 50 is smaller than the element
diffusion device 55. Due to the shaping optical system 20 and the
scanner 30, it is possible not only to regulate the shape and the
size of the spot area S on the light diffusion device 50, but also
to make uniform an illuminance distribution of the spot area S.
[0121] Thus, as shown in FIG. 5, the effective scanning section
sc1, in which the whole spot area S is located only within one
element diffusion device 55 corresponding to a predetermined
element illumination area Zp, can be made relatively long. On the
other hand, as shown in FIG. 5, the ineffective scanning section
scp2, in which only a part of the spot area S is located within the
one element diffusion device 55, i.e., in the illustrated example,
the ineffective scanning section scp2, in which the spot area Sp is
located over two element diffusion devices 55 that are adjacent in
the scanning direction sd, can be made relatively short. In the
example shown in FIG. 5, the effective scanning section sc1 is
significantly longer than the ineffective scanning section sc2.
Thus, even when only a predetermined element illumination area Zp
is illuminated, a period of time in which a laser light is emitted
can be increased. Thus, it is possible to illuminate the element
diffusion device 55 sufficiently brightly by means of the efficient
use of the laser light source 15, instead of using a high output
laser light source 15. Thus, the performance of the laser light
source 15 is sufficiently utilized so as to illuminate the
illumination area Z in a desired light distribution pattern with a
sufficiently bright quantity of light.
[0122] Particularly in the example shown in FIGS. 4 and 5, a size
wsx of the spot area S along a direction parallel to the scanning
direction sd of the spot area S is significantly smaller than a
size wsy of the spot area S along a direction orthogonal to the
scanning direction sd of the spot area S, in particular, smaller
than a half of the size wsy. In the direction parallel to the
scanning direction sd of the spot area S, the size wsx of the spot
area S is significantly smaller than a size wpx of the element
diffusion device 55, in particular, smaller than a half of the size
wpx. Thus, the ineffective scanning section sc2, in which only a
part of the spot area S is located within the one element diffusion
device 55, can be made very short. Therefore, according to the
example shown in FIGS. 4 and 5, a period of time in which the laser
light source 15 stops emission of laser light can be significantly
made short. That is to say, the laser light source 15 can be more
efficiently utilized.
[0123] In addition, as shown in FIG. 5, in the direction orthogonal
to the scanning direction sd of the spot area S, the size wsy of
the spot area S is substantially the same as or slightly smaller
than the size wpy of the element diffusion device 55. Thus, most of
the light diffusion device 50 can be irradiated with coherent
light, in conjunction with the operation of the scanner 30. Namely,
the whole surface of the light diffusion device 50 can be
efficiently utilized, so as to avoid enlargement of the
illumination device 10.
[0124] Further, adjustment of the shape of the spot area S and the
illuminance distribution in the spot area S by using the shaping
optical system 20 and the light condensing optical system 40 is
advantageous in terms of making speckles unnoticeable.
[0125] As shown in FIG. 5, by making smaller the size wsx of the
spot area S along the direction parallel to the scanning direction
sd of the spot area S, a period of time in which respective
positions of the element diffusion device 55 is irradiated with
coherent light can be made relatively short. That is to say, a
position from which illumination light toward each position of the
element illumination area Zp goes out switches for a short period
of time. In other words, an incident direction of the illumination
light toward each position of the element illumination area Zp
change rapidly. As a result, since speckle patterns are overlapped
over time, speckles can be effectively made unnoticeable.
[0126] In addition, as shown in FIG. 5, by making uniform the
illuminance distribution in the spot area S, speckles can be
effectively made unnoticeable at each instance. As shown in FIG. 6,
when the uniformity of illumination distribution in the spot area
Sp is low, a phase intensity from each position in the spot area Sp
toward one position Ps in the element illumination area Zp at a
given instance becomes non-uniform. Thus, since the overlap of
speckle patterns at each instance is insufficient, the speckle
reduction effect cannot be efficiently exerted in a sufficient
manner. On the other hand, as shown in FIG. 5, when the
illumination distribution in the spot area Sp is uniform, a phase
intensity from each position in the spot area S toward one position
Ps in the element illumination area Zp at a given instance can be
made uniform. Thus, since the overlap of speckle patterns at each
instance is effectively realized, the speckle reduction effect can
be efficiently exerted in a sufficient manner.
[0127] Particularly in the example shown in FIG. 5, the large size
wsy of the spot area S in the direction orthogonal to the scanning
direction sd of the spot area S is ensured. Thus, while the size
wsx of the spot area S in the direction parallel to the scanning
direction sd of the spot area S is small, broadness of the spot
area S can be effectively ensured. As a result, the overlap of
speckle patterns can be more effectively realized at each
instance.
[0128] As described above, in the first embodiment, the
illumination device 10 includes the shaping optical system 20 that
shapes coherent light, and the light condensing optical system 40
located on a light path of the coherent light from the shaping
optical system 20 up to the light diffusion device 50. The light
condensing optical system 40 condenses coherent light such that the
spot area S on the light diffusion device 50 is smaller than the
element diffusion device 55. Each element diffusion device 55
diffuses coherent light incident thereon so as to illuminate an
element illumination area Zp corresponding to the element diffusion
device 55. According to the first embodiment, the shape of the spot
area S and the illuminance distribution of the spot area S can be
adjusted by the shaping optical system 20 and the light condensing
optical system 40. As a result, the performance of the laser light
source 15 is sufficiently utilized so as to illuminate the
illumination area Z in a desired light distribution pattern with a
sufficiently bright quantity of light.
[0129] In addition, in the first embodiment, the shaping optical
system 20 divides coherent light emitted from the coherent light
source 15 into light fluxes lf2. The light condensing optical
system 40 adjusts light paths of light fluxes lf3 such that the
light fluxes f13 are at least partially overlapped on the light
diffusion device 50. Thus, even when an illuminance distribution of
the coherent light upon emission from the coherent light source 15
is non-uniform, since the illuminance distribution is divided and
overlapped, the illuminance distribution can be effectively made
uniform. In particular, when the illuminance distribution of the
coherent light upon emission from the coherent light source 15 is
the typical Gaussian distribution, the illuminance distribution is
planarly divided and overlapped, so that the illuminance
distribution can be significantly effectively made uniform. Thus,
the illumination area Z can be more brightly illuminated with a
desired light distribution pattern.
[0130] Further, in the first embodiment, the light condensing
optical system 40 is the lens 41 having the focus position Pf on
which the light diffusion device 50 is located. According to such a
light condensing optical system 40, although it has a simple
structure, light incident on the light condensing optical system 40
at a given instance can be condensed highly efficiently on the spot
area S on the light condensing optical system 40, so that the
illuminance distribution of the spot area S can be effectively made
uniform.
[0131] Further, in the first embodiment, the shaping optical system
20 includes the collimation lens 22, and the lens array 23 located
on a light path from the collimation lens 22 up to the light
condensing optical system 40. According to such a shaping optical
system 20, the optical axes d.sub.lf3 of the light fluxes lf3
incident on the light condensing optical system 40 can be made
parallel. In this case, by means of the light condensing optical
system 40 using the light condensing lens 41, the optical axes
d.sub.lf4 of the light fluxes, which have been shaped by the
shaping optical system 20, can be allowed to intersect on the light
diffusion device 50. Thus, the illuminance distribution of the spot
area S can be more effectively made uniform.
[0132] Further, in the first embodiment, the lens array 23 includes
the element lenses 24. The light fluxes lf2 emergent from the
element lenses 24 can be the same light distributions each other.
In this case, by means of the light condensing optical system 40
using the light condensing lens 41, the light fluxes which have
been shaped by the shaping optical system 20 can be highly
precisely overlapped with one another on the light diffusion device
50. Thus, the shape of the spot area S can be more precisely
adjusted, and the illuminance distribution of the spot area S can
be more effectively made uniform.
[0133] The aforementioned first embodiment can be variously
modified. Modification examples are described herebelow. In the
drawings used in the below description, a component that can be
similarly structured as that of the above embodiment has the same
reference number as the number used for the corresponding component
of the above embodiment, and redundant description is omitted.
[0134] In the aforementioned first embodiment, there is shown the
example in which the shaping optical system 20 includes the beam
expander 21, the collimation lens 22 and the lens array 23.
However, the present invention is not limited to this example. The
shaping optical system 20 may be made of a beam homogenizer 25 that
forms a uniform intensity distribution. As the beam homogenizer 25,
a member using diffractive optical elements (DOE) or a member using
an aspherical lens or a free-form surface lens can be employed.
[0135] In addition, in the aforementioned first embodiment, there
is shown the example in which the light diffusion device 50 is made
of the hologram storage medium 52. However, the present invention
is not limited to this example. For example, the light diffusion
device 50 may be made by using a lens array group in which the
respective element diffusion devices 55 constitute one lens array.
In this case, the lens array is provided for each element
distribution device 55, and the shape of each lens array is
designed such that each lens array illuminates an element
illumination area Zp in the illumination area Z. Positions of the
respective element illumination areas Zp are at least partially
different.
[0136] Further, in the aforementioned first embodiment, there is
shown the example in which the polygonal mirror 31 reflects a laser
light on a position apart from the element lens 24 by the focus
distance of the element lens 24 along the optical axis d.sub.24 of
the element lens 24. However, the present invention is not limited
to this example. In addition, in the aforementioned first
embodiment, there is shown the example in which the polygonal
mirror 31 reflects a laser light on a position apart from the light
condensing lens 41 by the focus distance of the light condensing
lens 41 along the optical axes d.sub.40 of the light condensing
lens 41. However, the present invention is not limited to this
example. For example, the light condensing lens 41 may be located
on a light path from the element lens 24 toward the scanner 30. In
addition, the lens array 23 including the element lenses 24 may be
located on a light path from the scanner 30 toward the light
condensing optical system 40.
[0137] Further, in the aforementioned first embodiment, there is
shown the example in which the laser light source 15 as a coherent
light source emits laser lights of different wavelength ranges.
However, the present invention is not limited to this example. The
coherent light source may be made as a light source that emits
coherent light of the same wavelength range.
[0138] Further, the above-described illumination device 10 may be
mounted on a conveyance, or installed at a predetermined location.
When it is mounted on a conveyance, the conveyance may be various
moving bodies such as a vehicle like an automobile, a flying body
like an aircraft, a train, a ship, a diving body and so on.
[0139] Although some modification examples of the first embodiment
have been described above, the modification examples can be
naturally combined and used.
[0140] Next, a second embodiment is described with reference to an
example shown in FIGS. 7 to 13.
[0141] FIG. 7 is a perspective view schematically showing an
overall structure of an illumination device 110. The illumination
device 110 illuminates an illumination area Z using coherent light
such as laser light (laser beam). The illumination device 110
includes, as a light source, a laser light source 115 that
oscillates laser light. The laser light source 115 oscillates laser
light that is coherent light. The illumination device 110 includes
a diffusion optical system 120, a scanner 130, a light condensing
optical system 140 and a light deflection device 150, which process
light emitted from the laser light source 115. In the example shown
in FIG. 7, the diffusion optical system 120, the scanner 130, the
light condensing optical system 140 and the light deflection device
150 are located in this order along a light path of laser light
from the laser light source 115, and they process laser light in
this order. As described in detail below, the illumination device
110 described herein can illuminate, with a large quantity of
light, the illumination area Z in a desired light distribution
pattern, while sufficiently utilizing the performance of the light
source 115 by means of optical actions in the diffusion optical
system 120 and the light condensing optical system 140. Herebelow
the respective constituent elements are sequentially described.
[0142] In the example shown in FIG. 7, the laser light unit 115
includes a plurality of light source units 117 that emit laser
light. The light source units 117 may be independently arranged, or
may be a light source module formed by arranging the light source
units 117 side by side on a common substrate. For example, the
light source units 117 have a first light source unit 117a that
oscillates light of a red emission wavelength range, a second light
source unit 117b that oscillates light of a green emission
wavelength range, and a third light source unit 117c that
oscillates light of a blue emission wavelength range. According to
this example, since three laser lights (laser beams) emitted from
the light source units 117a, 117b and 117c are overlapped,
illumination beams of various colors including a white illumination
beam can be generated.
[0143] Although an example in which the laser light source 115 has
the three light source units 117a, 117b and 117c having emission
wavelength ranges different from one another is described
herebelow, the present invention is not limited thereto. The laser
light source 115 may have two light units 117 having emission
wavelength ranges different from each other, or four or more light
units 117 having emission wavelength ranges different from one
another. In addition, in order to increase emission intensity, a
plurality of the light source units 117 may be provided for each
emission wavelength range.
[0144] As shown in FIG. 7, the illumination device 110 includes an
emission control unit 112 connected to the laser light source 115.
The emission control unit 112 controls emission timings of laser
lights (laser beams) emitted by the laser light source 115. In
particular, the emission control unit 112 can switch emission of
laser lights and stop of emission of laser lights from the light
source unit 117a, 117b or 117c, independently from other light
source units. The control of emitting or not emitting laser lights
by the emission control unit 112 is carried out based on scanning
timings of a plurality of laser lights by the scanner 130, in other
words, based on incident positions of laser lights on the light
deflection device 150. As described above, in the case where the
laser light source 115 can emit three laser lights, i.e., a red
laser light, a blue laser light and a green laser light, it is
possible to generate illumination light of a color that is a
combination of given two or more colors of red, blue and green, by
controlling an emission timing of each laser light.
[0145] The emission control unit 112 may control whether a laser
light is emitted from each light source unit 117 or not, i.e.,
ON/OFF of emission, or may switch blocking or not blocking of a
light path of a laser light having been emitted from each light
source unit 117. In the latter case, light shutter units, not
shown, may be disposed between the respective light source units
117 and the diffusion optical system 120, such that passage and
blockage of laser lights can be switched by the light shutter
units.
[0146] Next, the diffusion optical system 120 is described. The
diffusion optical system 120 diffuses laser light emitted from the
laser light source 115. In particular, the diffusion optical system
120 diffuses light from the light source (light-source light) such
that a cross-sectional area of the light immediately before it
enters the light condensing optical system 140 is larger than a
cross-sectional area of the light immediately before it enters the
diffusion optical system 120. The cross-sectional area of light is
an area occupied by a light path in a cross-section orthogonal to
an optical axis of the light. In addition, an optical axis is an
axis line in which an intensity of the light is highest. Thus, the
diffusion optical system 120 shapes, for example, incident light
into a divergent light flux or a convergent light flux.
[0147] FIG. 8 is a plan view showing the illumination device 110.
As shown in FIG. 8, the diffusion optical system 120 includes a
beam expander 121, a collimation lens 122 and a lens array 123, in
this order along a light path of laser light. The beam expander 121
shapes a laser light emitted from the laser light source 115 into a
divergent light flux. The collimation lens 122 reshapes the
divergent light flux generated by the beam expander 121 into
parallel light fluxes lf11. The lens array 123 includes a plurality
of element lenses 124 that are arranged on positions facing the
collimation lens 122. The element lenses 124 are positioned such
that an optical axis d.sub.124 of each element lens 124 is parallel
to an optical axis d.sub.122 of the collimation lens 122. In
addition, the element lenses 124 are arranged on a virtual face vl
that is orthogonal to the optical axis d.sub.122 of the collimation
lens 122. Each element lens 124 shapes a parallel light flux lf11,
which has been shaped by the collimation lens 122 and has entered
the element lens 124, into a convergent light flux lf12.
[0148] In the example shown in FIG. 8, the diffusion optical system
120 divides a laser light emitted from the laser light source 115
into a plurality of light fluxes lf12. The diffusion optical system
120 divides a laser light into light fluxes lf12 the number of
which is equal to the number of the element lenses 124 included in
the lens array 123. In the illustrated example, each element lens
124 shapes a parallel light flux lf11, which has been shaped by the
collimation lens 122 and has entered the element lens 124, into a
convergent light flux lf12. That is to say, respective light fluxes
lf12 divided by the diffusion optical system 120 are convergent
light fluxes. In addition, in the illustrated example, the element
lenses 124 have the same structures each other. Thus, light fluxes
f112 emitted from the element lenses 124 are the same light
distributions. For example, the light fluxes lf12 have the same
convergent angles and the same convergent positions, and optical
axes d.sub.lf12 of the light fluxes lf12 are parallel to one
another.
[0149] A plurality of the diffusion optical systems 120 may be
provided correspondingly to the respective light source units 117
included in the laser light source 115. Alternatively, the single
diffusion shaping optical system 120 capable of adjusting light
paths of laser lights from the light source units 117a, 117b and
117c may be provided. In the example shown in FIG. 8, the light
source units 117a, 117b and 117c may be aligned in the depth
direction of the sheet plane of FIG. 8, the beam expander 121 may
diverge a laser light only in a plane of the sheet plane of FIG. 8,
and the collimation lens 122 and the element lenses 124 of the lens
array 123 in the diffusion optical system 120 may respectively be
formed as cylindrical lenses extending to have a certain
cross-sectional shape in the depth direction of the sheet plane of
FIG. 8. According to this example, the light source units 117 can
share the collimation lens 122 and the lens array 123.
[0150] Next, the scanner 130 is described. The scanner 130 adjusts
a traveling direction of a laser light emitted from the laser light
source 115. The scanner 130 changes traveling directions of laser
lights with time. Due to the light path adjustment of the scanner
130, a laser light emitted from the laser light source 115 scans
the light deflection device 150. In the example shown in FIGS. 7
and 8, the scanner 130 is formed as a polygonal mirror 131 having
six reflection surfaces. When the polygonal mirror 131 is rotated
about its central axis line as a rotational axis line ra, a
reflection direction of light that has entered there from a certain
direction can be changed cyclically. The respective six reflection
surfaces of the polygonal mirror 131 are formed as flat surfaces.
Thus, as shown in FIG. 9, after three light fluxes lf13, which had
been shaped by the diffusion optical system 120, have been
reflected by the polygonal mirror 131 so that their traveling
directions have been changed, optical axes d.sub.lf13 of the light
fluxes lf13 remain parallel. FIG. 9 is a partially enlarged plan
view showing a light path succeeding to the scanner 130.
[0151] In particular, in the illustrated example, the light source
units 117a, 117b and 117c are aligned in a direction parallel to
the rotational axis line ra of the polygonal mirror 131 (see FIG.
7). The reflection surface of the polygonal mirror 131 includes,
along this rotational axis line ra, a first reflection unit 131a, a
second reflection unit 131b and a third reflection unit 131c. The
first reflection unit 131a reflects a laser light emitted from the
first light source unit 117a and cyclically changes a traveling
direction of the laser light in a plane orthogonal to the
rotational axis line ra. In addition, the second reflection unit
131b reflects a laser light emitted from the second light source
unit 117b, and the third reflection unit 131c reflects a laser
light emitted from the third light source unit 117c.
[0152] As shown in FIG. 8, the polygonal mirror 131 is positioned
with respect to the diffusion optical system 120, such that the
polygonal mirror 131 reflects light from the diffusion optical
system 120 on a focus position of each element lens 124 of the lens
array 123, or on a position close thereto. Thus, as shown in FIG.
9, light reflected from the polygonal mirror 131 substantially
becomes a divergent light flux lf13 whose divergent point is the
reflection surface of the polygonal mirror 131.
[0153] The scanner 130 is not limited to the illustrated polygonal
mirror 131. It is possible to use, as the scanner 130, an apparatus
that three-dimensionally changes in a biaxial direction a traveling
direction of light incident thereon from a certain direction. For
example, MEMS (micro electromechanical systems) such as a digital
micromirror device (DMD) may be used as the scanner 130.
[0154] Next, the light condensing optical system 140 is described.
The light condensing optical system 140 is located on a light path
of a laser light from the diffusion optical system 120 up to the
light deflection device 150. The light condensing optical system
140 optically processes a laser light diffused by the diffusion
optical system 120. The light condensing optical system 140
condenses an expanded laser light such that a spot area S on the
light deflection device 150, i.e., an area, which is irradiated
with a laser light on the light deflection device 150 at a given
instance, has a smaller planar dimension.
[0155] In the illustrated example, the light condensing optical
system 140 is formed by a light condensing lens 141 having a focus
Pf. The light condensing lens 141 is located on a light path of a
laser light from the scanner 130 toward the light deflection device
150. As described above, the diffusion optical system 120 divides a
laser light into light fluxes lf13. As shown in FIG. 9, the optical
axes d.sub.lf13 of the light fluxes lf13 are parallel to one
another. Thus, as shown in FIG. 9, because of a lens action of the
light condensing lens 141, optical axes d.sub.lf14 of three light
fluxes lf14 intersect on a position Px on a virtual face vlf that
is apart from the light condensing lens 141 by a focus distance
f.sub.140 of the light condensing lens 141 along an optical axis
d.sub.140 of the light condensing lens 141. In the illustrated
example, the light deflection device 150 is located on the virtual
face vlf that is apart from the light condensing lens 141 by the
focus distance f.sub.140 of the light condensing lens 141 along the
optical axis d.sub.140 of the light condensing lens 141. Thus, the
three light fluxes lf13 having been shaped by the diffusion optical
system 120 are overlapped at least partially on the light
deflection device 150, by the light condensing action of the light
condensing optical system 140.
[0156] A convergent angle .theta..sub.x of the optical axis
d.sub.lf14 of the convergent light flux lf14 in FIG. 9 depends on a
light path width of the overall light-source light before it enters
the light condensing lens 141. The light path width of the
light-source light can be adjusted by a width w.sub.lf11 (see FIG.
8) of the parallel light flux lf11 formed by the beam expander 121
and the collimation lens 122 of the diffusion optical system 120.
Thus, by suitably designing the beam expander 121 and the
collimation lens 122, the convergent angle .theta..sub.x of the
optical axis d.sub.lf14 of the convergent light fluxes lf14 can be
adjusted when the light fluxes lf14 enter a spot area S.
[0157] In particular, in the illustrated example, as shown in FIG.
9, the scanner 130 and the light condensing optical system 140 are
located such that the polygonal mirror 131 reflects a laser light
from the diffusion optical system 120 on a position apart from the
light condensing lens 141 by the focus distance f.sub.140 of the
light condensing lens 141 along the optical axis d.sub.140 of the
light condensing lens 141, or on a position close to the position.
Further, as described above, each of light fluxes lf13, which has
been reflected by the polygonal mirror 131 and has entered the
light condensing optical system 140, is a divergent light flux lf13
whose divergent point is located on the reflection surface of the
polygonal mirror 131, or close thereto. Thus, each light flux lf13
incident on the light condensing lens 141 passes through the light
condensing lens 141 so as to be converted to a parallel flux lf14.
As a result, the light fluxes lf14 having been shaped by the
diffusion optical system 120 irradiate the same area on the light
deflection device 150 by the light condensing function of the light
condensing optical system 140, i.e., the light fluxes lf14 are
overlapped on the light deflection device 150 highly precisely.
Since the scanner 130 changes traveling directions of laser lights
over time, a spot area S on which the light fluxes lf14 are
condensed by the light condensing optical system 140 changes its
position over time on the light deflection device 150.
[0158] A width wsx of the spot area S in FIG. 9 depends on a
distance between the light condensing optical system 140 and the
scanner 130, and a divergent angle .theta..sub.lf13 of a divergent
light flux lf13 that enters the light condensing optical system
140. In addition, the divergent angle .theta..sub.lf13 of the
divergent light flux lf13 depends on a convergent angle
.theta..sub.lf12 of the convergent light flux lf12 having been
shaped by the element lens 124 of the diffusion optical system 120.
Thus, by suitably positioning the light condensing optical system
140 and the scanner 130 and by suitably designing the element lens
124, the width wsx of the spot area S can be adjusted. In
particular, by suitably designing the element lens 124, the width
wsx of the spot area S can be adjusted while effectively avoiding
enlargement of the illumination device 110.
[0159] A plurality of the light condensing optical systems 140 may
be provided correspondingly to the respective light source units
117a, 117b and 117c included in the laser light source 115.
Alternatively, the single light condensing optical system 140
capable of adjusting light paths of laser lights from the light
source units 117a, 117b and 117c may be provided. For example, when
a laser light is diverged or converged only in a plane parallel to
the sheet plane of FIG. 9, the light condensing lens 141 forming
the light condensing optical system 140 may be a cylindrical lens
extending to have a certain cross-sectional shape in the depth
direction of the sheet plane of FIG. 8. According to this example,
the light condensing lens 141 can be shared by laser lights emitted
by the light source units 117a, 117b and 117c.
[0160] Next, the light deflection device 150 is described. The
light deflection device 150 adjusts a light path of light from the
light source unit 115 to direct the incident light to a
predetermined range so as to illuminate the predetermined range. To
be more specific, a laser light whose light path is adjusted by the
light deflection device 150 passes through an illumination area Z,
and then illuminates a predetermined range that is an actual
illumination range.
[0161] The illumination area Z and an element illumination area Zp
(see FIG. 11), which forms a part of the illumination area Z, are
illumination areas of near fields that are overlappingly
illuminated by respective element deflection devices 155 in the
light deflection device 150. An illumination range of a far field
is generally expressed as a diffusion angle distribution in an
angular space, rather than an actual illumination area size. The
terms "illumination area" and "element illumination area" in this
specification include a diffusion angle range in an angular space
in addition to an actual illumination area (illumination range).
Thus, a predetermined range illuminated by the illumination device
110 of FIGS. 7 and 10 can be an area that is greatly larger than
the illumination area Z of a near field shown in FIGS. 7 and
10.
[0162] FIG. 10 is a plan view showing the light deflection device
150. In the illustrated example, the light deflection device 150
includes the first light deflection device 150a, a second light
deflection device 150b and a third light deflection device 150c,
correspondingly to the fact that the laser light source 115
includes the first to third light source units 117a, 117b and 117c.
A laser light from the first light source unit 117a enters the
first light deflection device 150a, a laser light from the second
light source unit 117b enters the second light deflection device
150b, and a laser light from the third light source unit 117c
enters the third light deflection device 150c. By using the laser
lights that have entered the whole areas of the respective light
deflection devices 150a, 150b and 150c so that their light paths
are adjusted, the whole area of the common illumination area Z can
be illuminated.
[0163] Thus, the first light deflection device 150a directs red
light from the first light source unit 117a toward the illumination
area Z, the second deflection device 150b directs green light from
the second light source unit 117b toward the illumination area Z
and the third light deflection device 150c directs blue light from
the third light source unit 117c toward the illumination area Z,
whereby the illumination area Z can be illuminated in white. As
shown in FIG. 7, the light deflection devices 150a, 150b and 150c
are respectively formed to have an elongate shape in a direction
orthogonal to the rotational axis line ra of the polygonal mirror
131 forming the scanner 130. The light deflection devices 150a,
150b and 150c are arranged side by side in a direction orthogonal
to their longitudinal directions.
[0164] As shown by the dotted lines in FIG. 10, each of the light
deflection devices 150a, 150b and 150c has a plurality of element
deflection devices 155. Each element deflection device 155 has a
light path control function for directing a traveling direction of
light, which has been incident thereon from a certain direction,
toward a predetermined direction. For example, when lights enter
one element deflection device 155 from two different directions,
the lights from the respective directions go out from the element
deflection device 155 toward directions different from each other.
In addition, each element deflection device 155 has a light path
control function different from the other element deflection
devices 155. Thus, lights, which respectively have entered two
different element deflection devices 155 from the same direction,
go out from the element deflection devices 155 toward directions
different from each other.
[0165] In the illustrated example, when light has entered an
element deflection device 155 via the diffusion optical system 120,
the scanner 130 and the light condensing optical system 140, a
traveling direction of the light is bent by the element deflection
device 155, and the light travels to a predetermined element
illumination area Zp. Particularly in the second embodiment, light
is diffused by the diffusion optical system 120, then a light path
of the light is adjusted by the scanner 130, and the light further
is condensed by the light condensing optical system 140 so as to
enter the element deflection device 155. Namely, as shown in FIG.
9, light incident on an element deflection device 155 at a certain
instance has an incident direction distribution corresponding to
the dispersion angle .theta..sub.x of the optical axes d.sub.lf14
of the convergent light fluxes lf14. Thus, light emergent from the
element deflection device 155 at a certain instance also has an
angular distribution corresponding to a predetermined dispersion
angle .theta..sub.y. In addition, as shown in FIG. 9, light
incident on the element deflection device 155 at a certain instance
enters the whole area of the spot area S having an areal broadness
to a certain degree. Thus, the light incident on the element
deflection device 155 is diffused by the element deflection device
155, and can illuminate the whole area of a predetermined element
illumination area Zp.
[0166] An element illumination area Zp forms a part of the
illumination area Z. An element illumination area Zp corresponding
to one element deflection device 155 is not at least partially
overlapped with an element illumination area Zp corresponding to
another element deflection device 155. Namely, an aggregation of
the element illumination areas Zp corresponding to a plurality of
element deflection devices 155 provides the illumination area Z
that can be illuminated by the illumination device 110.
[0167] FIG. 11 is a plan view showing the element deflection
devices 155, together with the element illumination areas Zp to
which light is directed by the element deflection devices 155. In
the example shown in FIG. 11, nine element deflection devices 155
are aligned along the longitudinal directions of the respective
light deflection devices 150a, 150b and 150c. The illumination area
Z is planarly divided like a grid into nine element illumination
areas Zp. That is to say, in the illustrated example, one element
illumination area Zp is not overlapped with another element
illumination area Zp. First element deflection devices 155a of the
respective light deflection devices 150a, 150b and 150c illuminate
a first element illumination area Zp1. Similarly, second to ninth
element deflection devices 155b to 155i of the respective light
deflection devices 150a, 150b and 150c illuminate second to ninth
element illumination areas Zp2 to Zp9.
[0168] Since a traveling direction of a laser light is changed by
the scanner 130 over time, as shown in FIG. 10, the laser lights
(laser beams) scan the light deflection devices 150a, 150b and 150c
along the longitudinal directions of the light deflection devices
150a, 150b and 150c. As shown in FIG. 10, an area on the light
deflection device 150 irradiated with the laser light at a certain
instance, i.e., a spot area S has a planar dimension smaller than
the element deflection device 155. The spot area S scans the first
to ninth element deflection devices 155a to 155i sequentially.
[0169] The light deflection device 150 is formed with the use of a
diffraction grating array 152, for example. In the example shown in
FIGS. 7, 10 and 11, three diffraction grating arrays 152a, 152b and
152c are disposed correspondingly to the respective light
deflection devices 150a, 150b and 150c. The respective diffraction
grading arrays 152a, 152b and 152c are provided correspondingly to
laser lights of different wavelength ranges. By using laser lights
of wavelength ranges which have entered the whole area of the
respective diffraction grating arrays 152a, 152b and 152c so as to
be deflected, the whole area of the the common illumination area Z
can be illuminated.
[0170] Each of the diffraction grating arrays 152a, 152b and 152c
is segmented into a plurality of the element deflection devices
155. The respective element deflection devices 155 are formed of
diffraction gratings 157 storing interference fringe patters
different from one another. A laser light incident on each
diffraction grating 157 is diffracted by an interference fringe
pattern and illuminates a corresponding element illumination area
Zp in the illumination area Z. By variously adjusting the
interference fringe patterns, a traveling direction of a laser
light that is diffracted by each diffraction grating 157, in other
words, a traveling direction of a laser light that is deflected by
each diffraction grating 157 can be controlled.
[0171] The diffraction grating 157 can be manufactured as a volume
type hologram, for example. To be more specific, when a hologram
photosensitive material that is a matrix of the diffraction grating
157 is irradiated with reference light and object light of coherent
light interfering with each other, interference fringes by the
light interference are formed on the hologram photosensitive
material so that the diffraction grating 157 is manufactured.
[0172] By emitting laser light toward the element deflection device
155 such that the laser light travels reversely to the light path
of the reference light that was used when the diffraction grating
157 was manufactured, diffraction light goes out from the
diffraction grating 157 reversely along the light path of the
object light that was used when the diffraction grating 157 was
manufactured.
[0173] Instead of being formed by using real object light and
reference light, a complicated interference fringe pattern formed
on each diffraction grating 157 can be designed by using a computer
based on a wavelength and an incident direction of expected
illumination light to be reconstructed as well as a shape and a
position of an image to be reconstructed. A diffraction grating 157
thus obtained is also referred to as computer generated hologram
(CGH). In addition, a Fourier conversion hologram in which
respective points on each diffraction grating 157 have the same
diffusion angle properties may be generated by a computer. Further,
a size and a position of an actual illumination range may be set by
disposing an optical member such as a lens behind an optical axis
of an element illumination area Zp.
[0174] One of the advantages of providing the diffraction grating
157 as the element deflection device 155 is that a light energy
density of laser light can be decreased by diffusion. Another
advantage is that the diffraction grating 157 can be used as a
directional surface light source. In this case, as compared with a
conventional lamp light source (point light source), a luminance on
a light source surface for achieving the same illumination
distribution can be decreased. Thus, safety of laser light can be
improved. Namely, even when a person looks a laser light having
passed through the element illumination area Zp with his/her eyes,
the eyes are less affected as compared with a case in which a
person looks a single point light source with his/her eyes.
[0175] Next, an operation of the illumination device 110 as
structured above is described.
[0176] As shown in FIG. 7, based on a control signal from the
emission control unit 112, the respective light source units 117a,
117b and 117c oscillate laser lights (laser beams) of respective
wavelength ranges. Laser lights going out from the laser light
source 115 firstly travel toward the diffusion optical system 120.
In the example shown in FIG. 8, the laser lights of the respective
wavelength ranges are shaped into parallel light fluxes lf11 by the
beam expander 121 and the collimation lens 122 of the diffusion
optical system 120. Thereafter, each of the parallel light fluxes
lf11 of the respective wavelength ranges is divided into convergent
light fluxes lf12 by the element lens 124 of the lens array 123. As
to the laser lights of the respective wavelength ranges, the
convergent light fluxes lf12 are similarly shaped, and optical axes
of d.sub.lf12 of the convergent light fluxes lf12 are parallel to
one another.
[0177] The laser lights having been shaped by the diffusion optical
system 120, i.e., the convergent light fluxes lf12 travel toward
the polygonal mirror 131 forming the scanner 130. The polygonal
mirror 131 is consecutively rotated about the rotational axis line
ra. Thus, an inclination angle of the reflection surface of the
polygonal mirror 131 is cyclically changed within a predetermined
angular area. As a result, a direction of a laser light reflected
by the polygonal mirror 131 cyclically changes.
[0178] As shown in FIG. 8, the polygonal mirror 131 reflects the
convergent light fluxes lf12 on a position where the convergent
light fluxes lf12 converge, or on a position close thereto. Thus,
since the convergent light fluxes lf12 are reflected by the
polygonal mirror 131, the convergent light fluxes lf12 are
converted into divergent light fluxes lf13 whose divergent points
are located on the reflection position of the polygonal mirror 131,
or on a position close thereto. Each of the six reflection surfaces
of the polygonal mirror 131 is large enough to reflect all the
convergent light fluxes lf12 having been shaped by the diffusion
optical system 120. Thus, as shown in FIG. 9, optical axes
d.sub.lf13 of the divergent light fluxes lf13 that are the laser
lights reflected by the polygonal mirror 131 remain parallel. Since
the polygonal mirror 131 reflects the light fluxes lf13 that are in
the convergent state, enlargement of the polygonal mirror 131 can
be effectively avoided.
[0179] In addition, the polygonal mirror 131 includes the first
reflection unit 131a, the second reflection unit 131b and the third
reflection unit 131c, along this rotational axis line ra. Since
these reflection units 131a, 131b and 131c are synchronically
operated, the laser light from the first light source unit 117a,
the laser light from the second light source unit 117b and the
laser light from the third light source unit 117c synchronically
change their traveling directions.
[0180] As shown in FIG. 9, the divergent light fluxes lf13 with
their light paths having been adjusted by the scanner 130 enter the
light condensing optical system 140. The optical axes d.sub.lf13 of
the divergent light fluxes lf13 remain parallel to one another. In
addition, the light deflection device 150 is located on the focus
Pf of the light condensing lens 141 forming the light condensing
optical system 140. Thus, light fluxes lf14 with their light paths
having been adjusted by the light condensing lens 141 are condensed
by the light condensing lens 141, and their optical axes d.sub.lf14
intersect on the light deflection device 150. In particular, in the
illustrated example, the reflection position of the polygonal
mirror 131 is located on a focus position behind the light
condensing lens 141, or on a position close thereto. Thus, the
light fluxes lf13 traveling from the polygonal mirror 131 toward
the light condensing lens 141 are converted to parallel light
fluxes lf14 by the lens effect of the light condensing lens 141.
The parallel light fluxes lf14 are overlapped with one another on
the light deflection device 150.
[0181] An area on which the parallel light fluxes lf14 are
overlapped with one another on the light deflection device 150,
i.e., a spot area S scans the light deflection device 150 along the
longitudinal direction of the elongate light deflection device 150,
in conjunction with the operation of the scanner 130. As a result,
as shown in FIG. 10, the laser lights sequentially irradiate the
element deflection devices 155. The laser light incident on each
element deflection device 155 is deflected by the element
deflection device 155 so as to illuminate the whole area of an
element illumination area Zp corresponding to the element
deflection device 155.
[0182] The emission control unit 112 controls emission of laser
lights from the light source unit 117, depending on irradiation
positions of laser lights on the light deflection device 150. Thus,
only a desired element illumination area Zp in the illumination
area Z can be selected and illuminated. In addition, the emission
control unit 112 can control emission of light from the light
source units 117a, 117b and 117c independently. Thus, it is also
possible to illuminate a predetermined element illumination area Zp
with light emitted from one(s) selected from the first light source
unit 117a, the second light source unit 117b and the third light
source unit 117c. That is to say, each of the first to ninth
element illumination areas Zp1 to Zp9 included in the illumination
area Z can be adjusted independently from the other element
illumination areas, as to whether illuminated or not, the degree of
brightness and the color of illumination light.
[0183] In order to simplify control of the scanner 130, the scanner
130 is preferably operated such that a laser light can cyclically
scan the whole area of the light deflection device 150. In the
example shown in FIG. 10, the scanner 130 is preferably operated
such that a laser light scans over the whole lengths of the light
deflection devices 150a, 150b and 150c along the longitudinal
directions of the light deflection devices 150a, 150b and 150c.
When only a predetermined element illumination area Zp is desired
to be illuminated, the emission control unit 112 controls emission
and stop of laser light of the laser light source 115, depending on
the operation of the scanner 130, in other words, depending on a
position on the light deflection device 150 to be irradiated with a
laser light.
[0184] On the other hand, light emitted from a light source such as
a laser light source generally involves illuminance non-uniformity
in a spot area. Generally, as shown in FIG. 13, the center of the
spot area Sp is brightest, and it gradually darkens toward a
periphery of the spot area Sp. Typically, an illuminance
distribution is the Gaussian distribution from the center of the
spot area Sp toward the periphery thereof. Namely, the spot area Sp
has a large rim part of a low illuminance. Thus, as shown in FIG.
13, an effective scanning section scp1, in which the whole spot
area Sp is located inside one element deflection device 155
corresponding to a predetermined element illumination area Zp, is
relatively short. On the other hand, as shown in FIG. 13, an
ineffective scanning section scp2, in which only a part of the spot
area Sp is located within the one element deflection device 155,
i.e., in the example shown in FIG. 13, the ineffective scanning
section scp2, in which the spot area Sp is located over two element
deflection devices 155 that are adjacent in a scanning direction
sd, is relatively long. In the example shown in FIG. 13, the
effective scanning section scp1 is significantly shorter than the
ineffective scanning section scp2.
[0185] In the example shown in FIG. 13, when only a predetermined
element illumination area Zp is illuminated, the emission control
unit 112 emits a laser light in such a manner that the center of
the spot area Sp is located within the effective scanning section
scp1, while stops emission of laser light in such a manner that the
center of the spot area Sp is located within the ineffective
scanning section scp2. Thus, when the scanner 130 is operated at a
constant speed, in the example shown in FIG. 13, a time period in
which the emission of laser light is stopped is significantly long.
Namely, the laser light source 115 is not efficiently used.
Further, in order to illuminate an element illumination area Zp
sufficiently brightly by emitting light in a short period of time,
it is necessary to prepare a high output laser light source.
[0186] In order to deal with this problem, the illumination device
110 in the second embodiment is equipped with the diffusion optical
system 120 and the scanner 130. The diffusion optical system 120
shapes light-source light emitted from the laser light source 115.
The light condensing optical system 140 is located on a light path
of light from the diffusion optical system 120 up to the light
deflection device 150, and condenses light-source light such that
the spot area S on the light deflection device 150 is smaller than
the element deflection device 155. Due to the diffusion optical
system 120 and the scanner 130, it is possible not only to regulate
the shape and the size of the spot area S on the light deflection
device 150, but also to make uniform an illuminance distribution of
the spot area S.
[0187] Thus, as shown in FIG. 12, the effective scanning section
sc1, in which the whole spot area S is located only within one
element deflection device 155 corresponding to a predetermined
element illumination area Zp, can be made relatively long. On the
other hand, as shown in FIG. 12, the ineffective scanning section
scp2, in which only a part of the spot area Sp is located within
the one element deflection device 155, i.e., in the illustrated
example, the ineffective scanning section scp2, in which the spot
area Sp is located over two element deflection devices 155 that are
adjacent in the scanning direction sd, can be made relatively
short. In the example shown in FIG. 12, the effective scanning
section sc1 is significantly longer than the ineffective scanning
section sc2. Thus, even when only a predetermined element
illumination area Zp is illuminated, a period of time in which a
laser light is emitted can be increased. Thus, it is possible to
illuminate the element defection device 155 sufficiently brightly
by means of the efficient use of the laser light source 115,
instead of using a high output laser light source 115. Thus, the
performance of the laser light source 115 is sufficiently utilized
so as to illuminate the illumination area Z in a desired light
distribution pattern with a sufficiently bright quantity of
light.
[0188] Particularly in the example shown in FIGS. 10 and 12, a size
wsx of the spot area S along a direction parallel to the scanning
direction sd of the spot area S is significantly smaller than a
size wsy of the spot area S along a direction orthogonal to the
scanning direction sd of the spot area S, in particular, smaller
than a half of the size wsy. In the direction parallel to the
scanning direction sd of the spot area S, the size wsx of the spot
area S is significantly smaller than a size wpx of the element
deflection device 155, in particular, smaller than a half of the
size wpx. Thus, the ineffective scanning section sc2, in which only
a part of the spot area S is located within the one element
deflection device 155, can be made very short. Therefore, according
to the example shown in FIGS. 10 and 12, a period of time in which
the laser light source 115 stops emission of laser light can be
significantly made short. That is to say, the laser light source
115 can be more efficiently utilized.
[0189] In addition, as shown in FIG. 12, in the direction
orthogonal to the scanning direction sd of the spot area S, the
size wsy of the spot area S is substantially the same as or
slightly smaller than the size wpy of the element deflection device
155. Thus, most of the light deflection device 150 can be
irradiated with light-source light, in conjunction with the
operation of the scanner 130. Namely the whole surface of the light
deflection device 150 can be efficiently utilized, so as to avoid
enlargement of the illumination device 110.
[0190] As described above, in the second embodiment, the
illumination device 110 includes the diffusion optical system 120
that diffuses light-source light emitted from the light source, and
the light condensing optical system 140 located on a light path of
light-source light from the diffusion optical system 120 up to the
light deflection device 150. The light condensing optical system
140 condenses light-source light such that the spot area S on the
light deflection device 150 is smaller than the element deflection
device 155. Each element deflection device 155 adjusts a light path
of light-source light incident thereon so as to illuminate an
element illumination area Zp corresponding to the element
deflection device 155. According to the second embodiment, the
shape of the spot area S and the illuminance distribution of the
spot area S can be adjusted by the diffusion optical system 120 and
the light condensing optical system 140. As a result, the
performance of the laser light source 115 is sufficiently utilized
so as to illuminate the illumination area Z in a desired light
distribution pattern with a sufficiently bright quantity of
light.
[0191] In addition, in the second embodiment, the diffusion optical
system 120 divides light-source light emitted from the light source
115 into light fluxes lf12. The light condensing optical system 140
adjusts light paths of light fluxes lf13 such that the light fluxes
f113 are at least partially overlapped on the light deflection
device 150. Thus, even when an illuminance distribution of the
light-source light upon emission from the light source 115 is
non-uniform, since the illuminance distribution is divided and
overlapped, the illuminance distribution can be effectively made
uniform. In particular, when the illuminance distribution of the
light-source light upon emission from the light source 115 is the
typical Gaussian distribution, the illuminance distribution is
planarly divided and overlapped, so that the illuminance
distribution can be significantly effectively made uniform. Thus,
the illumination area Z can be more brightly illuminated with a
desired light distribution pattern.
[0192] Further, in the second embodiment, the light condensing
optical system 140 is the lens 141 having the focus position Pf on
which the light deflection device 150 is located. According to such
a light condensing optical system 140, although it has a simple
structure, light incident on the light condensing optical system
140 at a given instance can be condensed highly efficiently on the
spot area S on the light condensing optical system 140, so that the
illuminance distribution of the spot area S can be effectively made
uniform.
[0193] Further, in the second embodiment, the diffusion optical
system 120 includes the collimation lens 122, and the lens array
123 located on a light path from the collimation lens 122 up to the
light condensing optical system 140. According to such a diffusion
optical system 120, the optical axes d.sub.lf13 of the light fluxes
lf13 incident on the light condensing optical system 140 can be
made parallel. In this case, by means of the light condensing
optical system 140 using the light condensing lens 141, the optical
axes d.sub.lf14 of the light fluxes, which have been shaped by the
diffusion optical system 120, can be allowed to intersect on the
light deflection device 150. Thus, the illuminance distribution of
the spot area S can be more effectively made uniform.
[0194] In addition, by adjusting the width w.sub.lf11 (see FIG. 8)
of the parallel light flux lf11 by the beam expander 121 and the
collimation lens 122, a dispersion angle .theta. (see FIG. 10) of
the optical axes d.sub.lf14 of the convergent light fluxes lf14
incident on the light condensing lens 141 can be controlled. Thus,
it is possible to shape illumination light going out from the
element deflection device 155 to adjust a dispersion angle
.theta..sub.y of the illumination light. Further, it is possible to
adjust the size of a spot area S to be illuminated by the
illumination light, and a brightness distribution in the spot area
S.
[0195] Further, in the second embodiment, the lens array 123
includes the element lenses 124. The light fluxes lf12 emergent
from the element lenses 124 can be the same light distributions
each other. In this case, by means of the light condensing optical
system 140 using the light condensing lens 141, the light fluxes
which have been shaped by the diffusion optical system 120 can be
highly precisely overlapped with one another on the light
deflection device 150. Thus, the shape of the spot area S can be
more precisely adjusted, and the illuminance distribution of the
spot area S can be more effectively made uniform.
[0196] In addition, by suitably positioning the light condensing
optical system 140 and the scanner 130 and by suitably designing
the element lens 124 so as to adjust the convergent angle
.theta..sub.lf12 of the convergent light flux lf12 having been
shaped by the element lens 124, the width wsx (see FIG. 10) of the
spot area S can be controlled. In particular, by adjusting the
convergent angle .theta..sub.lf12 of the convergent light flux lf12
having been shaped by the element lens 124, the width wsx of the
spot area S can be adjusted while effectively avoiding enlargement
of the illumination device 110. Thus, it is possible to shape
illumination light going out from the element deflection device
155. Further, it is possible to adjust the size of a spot area S to
be illuminated by the illumination light, and a brightness
distribution in the spot area S.
[0197] The aforementioned second embodiment can be variously
modified. Modification examples are described herebelow. In the
drawings used in the below description, a component that can be
similarly structured as that of the above embodiment has the same
reference number as the number used for the corresponding component
of the above embodiment, and redundant description is omitted.
[0198] In the aforementioned second embodiment, there is shown the
example in which the diffusion optical system 120 includes the beam
expander 121, the collimation lens 122 and the lens array 123.
However, the present invention is not limited to this example. The
diffusion optical system 120 may be made of a beam homogenizer 125
that forms a uniform intensity distribution. As the beam
homogenizer 125, a member using diffractive optical elements (DOE)
or a member using an aspherical lens or a free-form surface lens
can be employed.
[0199] In addition, in the aforementioned second embodiment, there
is shown the example in which the light deflection device 150 is
made of the diffraction grating array 152. However, the present
invention is not limited to this example. For example, the light
deflection device 150 may be made by using a prism array in which
the respective element deflection devices 155 constitute one prism.
In this case, a prism is provided for each element deflection
device 155, and the shape of each prism is designed such that each
prism illuminates an element illumination area Zp in the
illumination area Z. Positions of the respective element
illumination areas Zp are at least partially different.
[0200] Further, in the aforementioned second embodiment, there is
shown the example in which the element deflection device 155 has a
light path adjustment function for directing a traveling direction
of light, which has been incident thereon from a certain direction,
toward a predetermined direction. However, not limited thereto, the
element deflection device 155 may have a diffusion property. For
example, the element deflection device 155 may direct a traveling
direction of light, which has been incident thereon from a certain
direction, toward a range having an angular distribution about a
predetermined direction. In this example, light emergent from the
element deflection device 155 may have a maximum luminance in a
predetermined direction, and a luminance of light emergent in a
direction inclined to the predetermined direction may decrease as
an inclination angle with respect to the predetermined direction
increases.
[0201] Further, in the aforementioned second embodiment, there is
shown the example in which the polygonal mirror 131 reflects a
laser light on a position apart from the element lens 124 by the
focus distance of the element lens 124 along the optical axis
d.sub.124 of the element lens 124. However, the present invention
is not limited to this example. In addition, in the aforementioned
first embodiment, there is shown the example in which the polygonal
mirror 131 reflects a laser light at a position apart from the
light condensing lens 141 by the focus distance of the light
condensing lens 141 along the optical axes d.sub.140 of the light
condensing lens 141. However, the present invention is not limited
to this example. For example, the light condensing lens 141 may be
located on a light path from the element lens 124 toward the
scanner 130. In addition, the lens array 123 including the element
lenses 124 may be located on a light path from the scanner 130
toward the light condensing optical system 140.
[0202] Further, in the aforementioned second embodiment, there is
shown the example in which the light condensing optical system 140
is formed of a convex lens. However, the present invention is not
limited thereto. For example, the light condensing optical system
140 may be formed of a concave mirror.
[0203] Further, in the aforementioned second embodiment, there is
shown the example in which the laser light source 115 as a light
source emits laser light (laser beams) of a plurality of wavelength
ranges. However, the present invention is not limited thereto. The
light source may be a light source that emits light of the same
wavelength range.
[0204] Further, the above-described illumination device 110 may be
mounted on a conveyance, or installed at a predetermined location.
When it is mounted on a conveyance, the conveyance may be various
moving bodies such as a vehicle like an automobile, a flying body
like an aircraft, a train, a ship, a diving body and so on.
[0205] Although some modification examples of the second embodiment
have been described above, the modification examples can be
naturally combined and used.
* * * * *